Online chat can mean anything from a traditional direct chat room interface to the newer Shoutbox implementations that add instant messaging (IM) capabilities to a site. In recent years, chat features have gained a somewhat dubious reputation because of their use by predators who seek to lure underage participants. Not a week goes by without some news feature or investigative piece airing on television that describes some villain using a chat room for bad purposes.

While a huge majority of chat rooms are certainly not dens of iniquity, the problem is significant enough that you should give it serious consideration before adding these capabilities to your site. The immediate interactive nature of an online chat makes it much more likely to be abused than other technologies where interaction is non-instantaneous and, the interaction is generally posted for the entire world to see.

You should also know about the legal implications if a bad person were to use your site for some form of crime.

A guestbook is one of the oldest forms of Web interaction. It allows visitors to post commentary and compliments on the contents of the board. Although a guestbook has little implementation cost in terms of time and energy, it also inspires the least community spirit. Therefore, a guestbook is a better addition to a traditional Web site than it is a feature used with most community sites.

The two most popular guestbook extensions for Joomla are Easybook and Jambook. Since a guestbook is fairly simple in both conception and implementation, these extensions provide very similar features. Your choice will likely be dependent on which extension most appropriately compliments the visual aspect of your site.

Easybook
Easybook is an excellent simple guestbook component. One of the best features of the component is the extensive anti-spam protection such as CAPTCHA (Completely Automated Public Turing Test to Tell Computers and Humans Apart) image generation, live email address confirmation checking, and automated word filter. The word filter list can be defined through the Administrator interface of the component and configured to automatically send an email to the administrator if someone attempts to post an item on the prohibited word list. Easybook can also be set to ping the supplied email server of the poster and ignore the post if the server isn’t valid.

Now that you possess the skills to program all three types of extensions (modules, components, and plug-ins), your development will probably require that you integrate any extension you create with the Joomla system. This means understanding how Joomla functions on an execution level, and likely being able to make calls to the Joomla framework.

 The complete Joomla framework is divided into a sizable number of packages, most of which are represented in an actual Joomla installation with a folder dedicated to the source files:

❑       Application Package — JApplication and related libraries are implemented as a factory class. The four classes extended from this package (JInstallation, JModel, JSite, and JAdministrator) make up the Joomla CMS application. Also included are the Data Access Object (DAO) libraries, including the abstract JModel class that is extended to create the classes JModelCategory, JModelComponent, JModelMenu, JModelModule, JModelPlugins, JModelSection, JModelSession, and JModelUser. It is located in the librariesjoomla directory.

Unlike modules that are all stored in the modules folder or components that all exist in the components folder, plug-ins are categorized and grouped within folders that define their categories. For example, plug-ins that provide search functionality are stored in the pluginssearch folder, while content plug-ins exist in the pluginscontent folder.

In the Plugin Manager, the category of plug-in is generally displayed in two places: as a prefix to the plug-in name and in the Type column. The name of each plug-in is preceded by the type. For example, the LDAP plug-in displays a name of “Authentication - LDAP.” The type of plug-in defines how the extension will be treated by the system.

The eight different types of plug-ins include the following:

In the 1980s, Ward Cunningham invented a new method of collaboration called a wiki, which is a Web site where visitors can add, edit, supplement, and remove articles from an encyclopedic store. The most famous example is an online encyclopedia known as Wikipedia (www.wikipedia.org). Users of the Web site have created or contributed to more than 2 million articles currently featured there.

Within the last decade, there has been incredible growth in the wiki phenomenon, especially related to technology. The open source community, in particular, benefits from the wiki Web sites, since many of the programmers of open source applications often lack the time to document their work. A wiki created to feature a particular application (such as the FreeMind mind-mapping tool) allows passionate users to add useful information, tips, and document parts of the program that aren’t self-explanatory.

Joomla is capable of hosting a wiki system through a component known as OpenWiki. OpenWiki is an extension adapted from the open source DokuWiki project (created by Andreas Gohr), which is a PHP application that provides wiki capabilities. OpenWiki is made to be fast and light, so while other wiki applications may include more features (such as the open source MediaWiki that is used for Wikipedia), OpenWiki consumes much fewer resources and provides much more responsiveness.